How Genetics May Affect Endurance Performance

Editor’s note: The following blog was originally posted on Triathlon & Multisport Magazine. You can follow them on Twitter @trimultimag. Travis Orth is a Physical Therapist at Athletico Willowbrook.

Triathlon is a sport that rewards hard work. And while we can all strive to be the best we can be, 99.9 per cent of us will never enjoy the view from the top step of the podium at a major endurance race. Why is this may have something to do with our genetics. Dr. Travis Orth sheds some light on recent research into a number of genes that may affect endurance performance.

Do our genes determine whether or not we will ever be able to clock a sub nine-hour Ironman? And will future genetic tests be able to predetermine the winner of endurance races? The more we learn about genes and how they influence our athletic ability, the closer we come to answering these questions. While we currently cannot prove or disprove the aforementioned questions, recent research on finishers at the Ironman World Championship and Ironman South Africa is shedding new light on the role our genetics plays in our triathlon performance. Data from these studies has indicated that there may be some predicting factors that influence our race finish times.

Two of the most widely studied genes regarding athletic performance are the angiotensin-converting enzyme gene (ACE) and α-actinin-3 gene (ACTN3).  The ACE gene has two variations that are found within human DNA, a truncated version noted as the deletion (D) version, and the full-length version designated as the insertion (I) version. Everyone has two copies of the ACE gene, one copy from your mother and one from your father. So, depending on which version of the gene you received from each of your parent your collection of the two could be one of three combinations: II, ID, or DD.

This gene was first studied in extreme high-altitude mountaineers back in 1998. These people require extreme levels of cardiovascular fitness to summit peaks in low oxygen environments. This original research demonstrated a correlation between having the I version of ACE and the ability to successfully climb to heights exceeding 8000 metres. Since publication of this study, numerous additional studies on ACE have been completed.

The connection with ACE and possible improved endurance performance makes studying this gene’s influence on an athlete’s performance in extreme endurance races such as iron-distance events, a prime target population. Previously, a correlation has been shown between having the I version and improved time at Ironman South Africa. This past year, additional data was published from this same sample population of Ironman athletes. This study went beyond the actual genetic level of investigation and looked at the plasma ACE activity levels in athletes’ blood. They found that there was a correlation between lower ACE activity levels, found in individuals with the I version, and improved performance at the Ironman. This data appears to suggest that decreased ACE activity levels may provide an advantage when completing extreme endurance events such as an ironman race.

Another study, which was published in 2013, examined the influence of the ACTN3 gene within competitors in the 2008 Ironman World Championship. This gene has also been widely studied and is found in two variations within humans; a 577R – which appears to confer improved sprinting ability, and a 577X – which seems to correlate to improved endurance capacity. Despite these previous correlations, the recent study did not find any association among the 196 athletes studies and improved performance times.

The confounding results between these two studies demonstrate how examining an athlete’s genetic profile in relation to endurance competition performance is not typically a linear comparison. The ability of an athlete to complete an ironman distance event relies on a multitude of factors, not only their genetics, but the athlete’s training, nutrition, swim, bike, and run technique, etc.  The complexity of these variables makes it very difficult to predict performance based purely on a genetic profile, especially that of a single gene. The results from the ACE study, although interesting, merely demonstrate an association between improved performance and having the I version, it does not establish a cause and effect. These results should not be interpreted as ‘if you contain two copies of the D version of ACE you will not be able to finish well at an Ironman distance event’, but rather at this time there seems to be more people finishing these races faster with the I version of ACE. Continued studies are needed to determine how the multitude of other genes known, and many that are still unknown, to influence athletic performance interact to help establish endurance performance.